Behavioral Parent Training (BPT) Interventions have proven efficacy for young children with externalizing behavior problems. However, not all families benefit, and ethnic minority families in particular are less likely to enroll, engage, and improve in BPT. The overarching goal of the proposed study is to develop and pilot test a personalization instrument, PersIn, that can be used to increase fit for culturally diverse familie in Parent Child Interaction Therapy (PCIT), an evidence based BPT intervention for young children. Personalization has the potential for significant public health impact because the approach is responsive to characteristics specific to individual families, and therefore can be used across a range of ethnic groups, including non-Hispanic Whites. We propose to maximize the impact of PersIn by personalizing on Parent Explanatory Model (PEM) parameters that have been found to vary across ethnic groups and which have been empirically demonstrated to impact treatment engagement and/or outcomes. In the first phase of the study, we will build on our previous experience culturally adapting BPTs and investigating therapist-client explanatory model match to develop PersIn. First, we will compile a proposed set of reliable, brief, and easy to use assessment instruments that clinicians could use to determine the parents' standing on each of the identified PEM personalization parameters. Second, we will identify an initial set of intervention adaptations that respond to extreme scores on each of these personalization parameters. Third, we will solicit feedback from a panel of experts in the cultural adaptation of BPT for each of three ethnic minority groups (Latino-, Asian-, and African-American) and modify PersIn according to their input. Fourth, we will conduct key informant interviews with clinicians with expertise with PCIT with diverse families to assess their perception of the likely effectiveness, appeal, and feasibility of each of the adaptations, and we will refine PersIn based on this feedback. Finally, Dr. Sheila Eyberg, creator of PCIT, will provide a final fidelity check o ensure that PersIn adaptations are consistent with the underlying theoretical model of the intervention and PersIn will be programmed for use on a tablet computer. In the second phase, we will conduct a pilot test of PersIn + PCIT with a sample of (N=28) families with a preschooler with externalizing programs from a wide range of ethnic backgrounds to determine if PersIn can be implemented with fidelity, can measurably increase PEM-treatment match, and that PEM-treatment match is related to engagement and outcomes in PCIT. A comparison between treatment elements of PersIn + PCIT and standard PCIT from a previous trial will be conducted to determine whether the two treatment conditions can be reliably differentiated from one another. Results from the pilot trial will be used as the basis of a larger R01 application to compare PCIT + PersIn to the standard version of PCIT and treatment as usual among a multicultural population.